Just days after his appointment to the board of Research In Motion, India-born Prem Watsa's company Fairfax Financial Holdings has increased stake in the Blackberry maker to 5.12%.

Fairfax owns 26.85 million shares of RIM, maker of BlackBerry smartphone, representing 5.12% stake in the company, up from 11.8 million shares in September, according to a filing with the US Securities and Exchange Commission.

Going by rough estimates, the stake buyout would have cost about $437 million Canadian dollars.

Earlier during the week, Watsa was named a RIM director as part of a management shakeup that included the replacement of co-Chief Executive Officers Jim Balsillie and Mike Lazaridis with former operating chief Thorsten Heins.